Morphine increases the activity of midbrain dopamine neurons in vitro

Michael E. Trulson, Kamyar Arasteh

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Morphine produced a dose-dependent increase in the activity of dopamine-containing neurons in the substantia nigra and ventral tegmental area recorded from mouse brain slices in vitro. The response was not changed in a low calcium/high magnesium incubation medium, indicating that the observed effects are the result of the direct action of morphine on dopamine neurons. Furthermore, a specific opiate antagonist, naloxone, versed the excitatory effects of morphine in both brain regions, while naloxone alone had no significant effect on the activity of dopaminergic neurons. Morphine was more potent on ventral tegmental area than substantia nigra dopamine neurons. β-Endorphin excited ventral tegmental area neurons but not substantia nigra cells, while [Leu5]enkephalin activated cells in both nuclei. These latter responses were blocked by naloxone. These data suggest that midbrain dopamine neurons contain receptors for opiates, and that ventral tegmental area neurons are more sensitive to the action of opiates than substantia nigra neurons.

Original languageEnglish
Pages (from-to)105-109
Number of pages5
JournalEuropean Journal of Pharmacology
Issue number1
StatePublished - 7 Aug 1985
Externally publishedYes


  • Dopamine
  • In vitro
  • Morphine
  • Single units
  • Substantia nigra
  • Ventral tegmental area


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